Variable modified with custom editor not saved when enter play mode, even with serialized attributes.

Hello!

I read a lot of forums and questions for this problem but I'm still unable to find out the solution.

I modify a variable on a prefab from a custom editor on anothe prefab. I used all the [System.Serializable] on my custom classes but the variable is still not saved when enter in play mode.

Here my code (I simplified it to keep only the essential informations) :

Custom editor script for Arena script :

 [CustomEditor(typeof(Arena))]
 public class ArenaEditor : Editor
 {
     public override void OnInspectorGUI()
     {
         DrawDefaultInspector();
 
         Arena arena = (Arena)target;
 
         if (GUILayout.Button("Action"))
         {
             foreach (Wave wave in arena.fight.waves)
             {
                 foreach (SpawnerData spawnerData in wave.spawnersData)
                 {
                         spawnerData.ID = 1;
                 }
             }
 
         if (GUI.changed)
         {
             EditorUtility.SetDirty(target);
         }
     }
 }

Arena script:

 [System.Serializable]
 public class Arena : MonoBehaviour
 {
     public Fight fight;
 }

Fight script :

 [System.Serializable]
 public class SpawnerData
 {
     public int ID;
 }
 
 [System.Serializable]
 public class Wave
 {
     public SpawnerData[] spawnersData;
 }
 
 [System.Serializable]
 public class Fight : MonoBehaviour
 {
     public Wave[] waves;
 }

The Arena script is on an Arena prefab instancied in the scene. This prefab references a Fight script on a Fight prefab instance in the scene too.

When I use the button on the Arena prefab instance, the ID is set to 1 on the Fight prefab. But when I enter "play" mode, the value is reset to 0.

I saw the ID value doesn't become "bold" when it changes to 1, I don't know if it means it won't be saved...

Thanks if you can bring any help to me !